The number of businesses offering health insurance to Connecticut workers declined over the decade ending in 2013, the latest figures from a public heath foundation show.

Research from the Robert Wood Johnson Foundation of Princeton, N.J., showed that the drop was primarily driven by small businesses, while most large businesses continued to offer coverage.

Workers also paid more money for employer-sponsored health insurance in Connecticut, and nationally, both in terms of actual dollars and as a percentage of health-insurance premiums, the foundation said.

An analysis Thursday looked at the average statistics for each of three two-year periods: 2004-2005; 2008-2009; and 2012-2013. The foundation found that deductibles were higher and premiums more expensive for employer-based health insurance, and that the recession accelerated the trend.

In the 2004-05 period, 56.5 percent of small businesses in Connecticut offered health coverage, falling to 39.4 percent eight years later, the report said.

During the entire decade, form 2004 to 2013, the vast majority of large employers — 98 percent — offered coverage to workers in Connecticut.

Nationally, during the same period, the percentage of small businesses offering health insurance fell from 42.7 percent of businesses to 35 percent, while large businesses remained largely flat, at 96 percent.

In Connecticut, the price of employer-sponsored health insurance for a single worker jumped 45 percent, from $4,127 to $5,968. Premiums for family coverage through an employer increased 48 percent, from $11,376 to $16,883.

Though the inflation rate for health insurance plans was more for families than individuals in Connecticut, the percent change in price was greater for families in the U.S overall than in Connecticut.

Nationally, premiums for a single-person's employer-sponsored health insurance plan rose 42 percent to $5,478. For a family, premiums increased 57 percent, to $16,302, according to the foundation's research.

Connecticut families, however, are paying a greater share of their coverage when compared with what individuals are paying. An individual worker in Connecticut paid 23.6 percent in of his or her employer-based insurance premium in 2012-13, up from 18.6 percent eight years earlier. People who have family health plans paid 28.5 percent of their employer-sponsored premiums in 2012-2013, up from 20.9 percent eight years earlier.

"Most Americans still get health insurance through their jobs, but this has been declining for more than a decade," Katherine Hempstead, who directs coverage issues at the Robert Wood Johnson Foundation, said in a statement. "It will be interesting to see how that trend evolves now that there are more opportunities for coverage through the individual market and Medicaid."

The way people buy health insurance is changing, in part because of rising medical costs, but also due to changes in employer-sponsored health insurance and mandates in the Affordable Care Act. The act, often called Obamacare, created public health insurance exchanges. States had the choice of either allowing people to shop for coverage on a federal site, healthcare.gov, or creating a state-based exchange. In Connecticut, the state exchange is Access Health CT.

"A lot of the data here pre-dates the exchange in terms of the trends it's showing," said Jason Madrak, chief marketing officer for Access Health CT, the public health insurance exchange for Connecticut.

"You had an awful lot of people kind of floundering out there without access to coverage, and then, God forbid, you were a person who had a pre-existing condition or something else. You might have had no options," he said.

Madrak said the exchange is a good backstop and safety net for people who were vulnerable because they lost a job or lost medical coverage.